The present invention relates to an undercoating composition for photolithographic resist in the manufacture of various kinds of electronic devices such as semiconductor devices and liquid crystal display panels. More particularly, the invention relates to a coating composition for the formation of an undercoating layer between the surface of a substrate and a layer of a photoresist composition which is patterned by patternwise exposure to actinic rays such as excimer laser beams to give a patterned resist layer having an excellently orthogonal cross sectional profile without irregularity such as trailing skirts and notchings.
In the patternwise exposure of a photoresist layer on a substrate surface with actinic rays in the manufacture of very fine semiconductor devices by utilizing the photolithographic technology for patterning of the photoresist layer, a problem is encountered that the resist layer obtained by patterning has a more or less irregular cross sectional profile by the influences of the standing waves due to the reflection of the exposure light at the substrate surface disadvantageously affecting the results of the subsequent processes utilizing the patterned resist layer as a masking. It is conventionally practiced accordingly to provide an antireflection film as an undercoating layer between the substrate surface and the photoresist layer with an object to solve this problem.
Along with the trend in the electronic technology toward more and more increasing fineness of semiconductor devices such as integrated circuits, the actinic rays for patternwise exposure of the photoresist layer is also under continuous shift toward those of a shorter wavelength such as KrF and ArF excimer laser beams as well as X-rays and electron beams. When excimer laser beams are used as the exposure light, the antireflection film on the substrate surface is formed by using a variety of undercoating compositions comprising, as the essential ingredients, a film-forming resinous compound, a light-absorbing compound to absorb the reflecting light from the substrate surface and a crosslinking agent to effect thermal crosslinking of the ingredients. In Japanese Patent Kokai 8-87115, 9-292715 and 10-228113, for example, an undercoating composition is disclosed which contains a crosslinking agent substituted by hydroxyalkyl groups and/or alkoxyalkyl groups, a dye compound selected from benzophenone compounds, diphenylsulfone compounds and sulfoxide compounds as the light-absorbing agent and an acrylic resin as the film-forming ingredient.
Investigations are now under way to develop a film-forming resin which is imparted with light-absorptivity by introducing light-absorbing substituent groups to the skeletal structure of the resin molecules. Examples of an undercoating composition containing such a dual-service resinous compound heretofore proposed include the antireflection undercoating compositions comprising two essential ingredients exemplified by the antireflection undercoating composition disclosed in Japanese Patent Kokai 10-204328 which contains a resin as a binder having quinolinyl groups, optionally, substituted by a heterocyclic group with an atom of nitrogen, oxygen or sulfur as the heteroatom, phenanthrenyl groups, acridinyl groups or alkyleneanthryl groups and a crosslinking agent such as glycoluril and the antireflection undercoating composition disclosed in WO 97/07145 which contains a resin obtained by the polymerization of a dye compound substituted by a group having an anthracene ring or naphthalene ring with an epoxy resin and a crosslinking agent such as melamine, urea, benzoguanamine and glycoluril.
Although the antireflection undercoating film formed by using the above described undercoating compositions is in fact effective to some extent for improving the cross sectional profile of the patterned resist layer formed thereon by suppressing the adverse influences of the standing waves at least when fineness of resist patterning is within a conventional range, the improvements obtained thereby are not quite satisfactory when further upgrading is required for the accuracy and fineness of the patterned resist layer resulting in irregularity in the cross sectional profile of the patterned resist layer such as skirt trailing and notching at the base part of the resist layer in contact with the substrate surface not to give an excellently orthogonal cross sectional profile.
A problem recently raised in connection with an antireflection undercoating composition containing a light-absorbing compound as a separate ingredient is contamination of various parts of the apparatuses by the deposition of the light-absorbing compound which is sometimes liable to sublimation.
Besides, a further proposal is made in Japanese Patent Kokai 10-301268 for an antireflection coating composition comprising hexamethoxymethyl melamine, propyleneglycol monomethyl ether acetate and 2,4-dimethylbenzene sulfonic acid, which, however, does not give an antireflection undercoating film capable of fully suppressing the adverse influences of standing waves and controlling the cross sectional profile of the patterned resist layer.